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THE  BLUE  HILL 


'EOROLOGICAL  OBSERVATORY. 


,N  ACCOUNT  OF  ITS  FOUNDATION  AND  WORK. 


THE  BLUE  HILL 


METEOROLOGICAL  OBSERVATORY. 


AN  ACCOUNT  OF  ITS  FOUNDATION  AND  WORK. 


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AN   ACCOUNT 


FOUNDATION  AND  WORK 


BLUE    HILL 


METEOKOLOGICAL  OBSERYATOKY. 


A.   LAWRENCE  EOTCH,   S.  B., 

Member  of  the  German  Meteorological  Society  and   Fellow  of  the  Royal  (London) 
Meteorological  Society. 


BOSTON: 

ALFRED     MUDGE     &     SON,     PRINTERS 

24   FRANKLIN    STREET. 

1887. 


15214 


THE  BLUE  HJLL 

METEOROLOGICAL  OBSERVATORY. 


OBJECT   OF   THE   OBSERVATORY. 

THE  study  of  high-level  meteorology  is  an  important  one, 
but  to  which  little  attention  has  been  given  in  this  country.  It 
is  true  that  the  United  States  Signal  Service  station  on  Mount 
Washington  was  the  first  complete  mountain  station  in  the 
world,  and  that  the  station  on  Pike's  Peak  is  still  the  highest, 
but  the  observations  have  not  been  published  in  extenso.  Ex- 
cepting these  two  stations,  the  writer  does  not  know  of  a  single 
meteorological  station  in  the  United  States  elevated  distinctly 
above  the  surrounding  country.  It  is  not  so  in  Europe.  The 
writer  visited,  in  1885,  nine  mountain  stations  situated  at  heights 
ranging  from  3,740  to  9,440  feet,  whose  observations  are  pub- 
lished in  a  comprehensive  manner;  and  a  number  of  other 
mountain  stations  exist.  The  French  observatories,  in  partic- 
ular, have  been  especially  constructed  for  their  purpose,  and 
equipped  with  registering  instruments,  at  a  large  cost,  which 
the  additions  to  our  knowledge  of  the  physics  of  the  upper  at- 
mosphere obtained  from  them  amply  repay.  (See  "The 
Mountain  Meteorological  Stations  of  Europe,"  by  A.  Lawrence 
Rotch,  in  American  Meteorological  Journal,  Vol.  II.,  Nos.  10, 
11,  and  12,  and  Vol.  III.,  No.  1.) 

Prof.  W.  M.  Davis,  in  an  article  in  /Science,  Vol.  V.,  No. 
121,  p.  440,  says:  "At  the  level  of  Pike's  Peak  the  cyclonic 
rotation  of  the  winds  is  hardly  observable,  the  observatory 
there  being  above  the  strata  of  the  atmosphere  whose  circula- 
tion is  seriously  disturbed  by  passing  storms.  On  Mount 
Washington  the  winds  whirl  round  almost  in  a  circle  about  the 
progressing  storm  centre.  At  Blue  Hill  we  may  hope  to  dis- 


4  THE    BLUE    HILL 

cover  the  true  circulation  of  the  lower  air,  unaffected-  by  the 
natural  or  artificial  irregularities  of  surface  that  modify  the 
records  of  so  many  of  our  Signal  stations.  The  value  of  obser- 
vations taken  at  moderate  elevations  is  attested  by  the  increas- 
ing number  of  mountain  observatories  in  Europe.  .  .  .  As 
Blue  Hill  has  the  first  private  observatory  of  the  kind  in  this 
country,  we  shall  look  with  especial  interest  for  the  results  of 
studies  based  upon  its  records." 

The  original  plan  was  to  use  the  Observatory  on  Blue  Hill 
only  for  special  investigations  in  meteorology,  leaving  the  regu- 
lar observations  to  be  carried  on  by  the  Signal  Service,  the 
writer  reserving  the  right  to  occupy  the  station  or  to  close  it  to 
the  Government  by  giving  due  notice.  The  Chief  Signal  Officer, 
however,  refused  to  enter  into  an  agreement  to  furnish  observers, 
unless  the  entire  control  was  given  to  the  Signal  Office  for  a 
period  of  not  less  than  two  years.  The  writer  therefore  deter- 
mined to  conduct  the  observations  himself.  The  proposed  work 
of  the  Blue  Hill  Observatory  was  stated  by  the  writer,  in  a  paper 
read  at  the  first  meeting  of  the  New  England  Meteorological  So- 
ciety, Oct.  21,  1884,  to  be  as  follows  :  "  The  investigation  of  the 
rainfall  at  this  elevation,  the  velocity  and  direction  of  the  vdnd, 
the  maximum  and  minimum  temperatures,  the  paths  of  thunder 
and  other  local  storms,  and  such  other  phenomena  as  may  present 
themselves.  It  has  been  suggested  that  atmospheric  electricity 
could  well  be  studied  here,  and  for  seismometric  apparatus  the 
situation  of  the  station  would  secure  absolute  freedom  from  the 
jar  and  vibration  incident  to  the  passage  of  neighboring  trains 
and  vehicles."  It  will  be  seen  from  the  account  of  the  work  of 
the  Observatory,  that  these  investigations,  with  the  exception 
of  the  last,  have  been  undertaken,  together  with  several  others. 


THE   SITE  OF  THE  OBSERVATORY. 

The  Blue  Hills,  situated  in  Norfolk  County,  Massachusetts, 
about  ten  miles  south  of  Boston  State  House,  are  the  nearest 
mountain  range  to  Boston  ;  and  though  their  elevations  are  not 
high,  the  fact  that  the  surroufiding  country  is  low  makes  them 
count  for  nearly  their  full  height.  Great  Blue  Hill,  the  highest 


METEOROLOGICAL  OBSERVATORY.  5 

of  the  range,  has  an  elevation  of  six  hundred  and  thirty-five 
feet,  and  is  not  only  the  highest  land  in  eastern  Massachusetts, 
but  is  also  the  highest  point  within  ten  miles  of  the  Atlantic 
coast  from  Maine  to  Florida.  As  Great  Blue  Hill  exceeds  the 
other  summits  of  the  range  by  more  than  one  hundred  feet,  it 
has  the  nature  of  an  isolated  hill,  commanding  an  unbroken 
view  of  the  sea-level  horizon,  thirty-three  miles  distant,  the 
New  Hampshire  mountains,  seventy  miles  away,  and  a  hun- 
dred and  twenty  towns  and  villages.  The  situation  is  thus 
admirable  for  a  meteorological  station ;  and  the  idea  of  estab- 
lishing one,  which  occurred  to  the  writer  in  August,  1884, 
being  encouraged  by  Eev.  A.  K.  Teele  of  Milton  and  Prof. 
W.  H.  Niles  of  Cambridge,  an  acre  of  land  on  the  south 
side  of  the  Hill,  and  a  small  amount,  including  the  highest  point 
on  which  were  the  ruins  of  the  old  lookout,  was  purchased 
with  difficulty.  Other  land  has  since  been  bought,  so  that 
there  are  now  some  sixty  acres  about  the  Observatory.  The 
top  of  the  Hill  comprises  several  acres  of  nearly  barren  ground, 
which  culminates  in  a  rocky  ledge,  fifteen  or  twenty  feet  above 
its  general  level.  The  dividing  line  between  Milton  and  Can- 
ton was  decided  by  the  selectmen  of  these  towns  to  pass 
over  the  ledge,  just  south  of  the  site  of  the  Observatory  tower, 
placing  the  latter  in  Milton  and  the  main  building  in  Canton. 
Although  careful  search  was  made  under  the  ruins  of  the  look- 
out for  the  copper  bolt,  set  by  Simeon  Borden,  about  1832, 
for  the  Massachusetts  Trigonometrical  Survey,  it  was  not 
found.  Its  position  was,  however,  known  to  be  26.25  feet 
N.  15°  37'  E.  of  the  bolt  fixed  by  the  Coast  Survey  in  1844, 
which  is  in  plain  view,  and  a  brass  plate  on  the  lower  floor  of  the 
tower  now  marks  the  site  of  the  Borden  bolt,  2.2  feet  below 
it,  in  latitude  42  12'  44"  N.,  longitude  71°  6'  53"  W.,  and 
635.05  feet  above  mean  tide.  Surveys  made  by  Mr.  E.  G. 
Chamberlain  and  by  students  of  the  Institute  of  Technology 
confirm  the  height  as  sufficiently  accurate. 

There  were  two  foot-paths  leading  from  the  Canton  road  to 
the  summit,  which  united  about  a  quarter  of  a  mile  below  it. 
It  was  decided  to  improve  the  path  starting  at  the  'Great 
Oak'  opposite  Brush  Hill  road,  and  accordingly,  on  Sept.  1, 


G  THE    BLUE    HILL 

twenty  men  began  work  on  it,  and  in  ten  days  had  completed 
a  fair  carriage  road  to  the  top,  having  a  length  of  jjj  -mile  and 
an  aver;ige  grade  of  about  1  in  10.  The  Hill  is  easily  acces- 
sible, as,  from  the  foot  of  this  road,  it  is  only  a  mile  and  a 
half  to  the  Readville  station,  reached  in  half  an  hour  from 
Boston  by  two  railroads.  Readville  is  the  railroad  station  and 
post-office  for  the  Observatory. 

The  accompanying  map  of  the  western  portion  of  the  Blue 
Hills,  prepared  under  the  supervision  of  Rev.  A.  K.  Teele,  for 
his  forthcoming  History  of  Milton,  is  kindly  allowed  to  be 
published  here.  It  should  be  stated  that  the  '  House  to  be 
erected  for  the  New  England  Meteorological  Society,'  which 
appears  on  this  map,  represents  the  Observatory. 

THE   BUILDING. 

Many  were  the  speculations  concerning  the  building  to  be 
erected  on  Blue  Hill,  some  saying  it  was  a  fort,  others  that  it 
was  a  monastery,  but  the  majority  believed  it  to  be  a  station 
for  the  Signal  Service.  There  were  no  stations  in  this  country 
which  could  be  taken  as  models,  and  the  design  was  left  mainly 
to  the  architects,  Messrs.  Rotch  and  Tilden,  who  fixed  the  cost 
at  $3,500.  The  contractors,  J.  H.  Burt  &  Co.,  commenced 
work  Oct.  18,  1884,  and  made  rapid  progress  during  the  fine 
autumn  weather.  By  Dec.  6  the  building  was  roofed  in,  render- 
ing the  workmen  independent  of  the  weather,  which  had  now 
become  cold  and  stormy.  The  outside  pointing  and  some  of 
the  masonry  were  left  until  spring.  Plastering  was  begun  Dec. 
22,  and  on  Jan.  31,  1885,  the  writer  and  his  observer  moved  in. 

The  Observatory  is  built  of  the  broken  stone  found  on  the 
Hill,  with  granite  trimmings.  It  consists  of  a  two-story  circular 
tower  of  twelve  feet  inside  diameter,  twenty-five  feet  high 
with  a  flat  roof,  which  contains  the  instruments.  Extending 
southward  from  this  tower  is  a  one-story  hip-roof  house,  with 
two  bedrooms,  a  dining-room  and  kitchen.  A  wooden  shed 
adjoins.  In  the  construction  every  precaution  was  taken  to 
insure  solidity,  the  walls  being  twenty  inches  thick,  and  the 
roof  well  anchored  to  them.  It  has,  however,  been  found  iin- 


METEOROLOGICAL  OBSERVATORY.  7 

possible  to  make  the  walls  impervious  to  rain,  which  is  driven 
by  heavy  gales  through  the  minute  cracks  which  the  stone 
must  contain.  Several  coats  of  marine  varnish  have  served  to 
disfigure  the  stone- work,  but  not  to  render  it  water-proof.  The 
walls  of  the  living-rooms  are  plastered  and  the  floors  are  of 
hard  pine.  In  the  cellar  is  a  wooden  tank-,  holding  nine 
hundred  gallons  of  water,  obtained  from  the  rain  falling  on  the 
roof,  which  has  always  proved  sufficient  for  domestic  purposes. 
A  spring  furnishes  water  for  drinking.  A  large  stove  in  the 
lower  room  of  the  tower  heats  the  upper  room  through  a 
register,  and  by  its  flue  and  that  of  the  kitchen  range  warms 
the  other  rooms  also.  About  ten  tons  of  coal  are  burnt 
annually.  Double  windows  are  put  on  throughout  the  building 
in  winter.  A  safe  built  into  the  chimney  protects  the  records 
and  charts  from  fire.  A  telephone  line  extends  clown  the  south 
side  of  the  Hill  to  the  central  office  in  Milton.  There  are  no 
houses  within  a  mile  of  the  Observatory,  so  that,  even  with  this 
connection  with  civilization,  it  is  largely  dependent  on  its  own 
resources. 

The  accompanying  photographs  of  the  Observatory  and  Hill 
were  taken  by  Sergt.  O.  B.  Cole,  of  the  Boston  Signal  station. 


THE   INSTRUMENTS. 

When  first  opened,  the  Observatory  had  the  instruments  of  a 
first-class  Signal  station.  Since  then,  many  self-recording  and 
other  instruments  have  been  added,  several  being  brought  from 
Europe  last  year  by  the  writer.  All  the  elements  observed, 
with  the  exception  of  the  force  of  the  wind,  the  kind  of  clouds 
and  their  direction  of  motion,  are  now  recorded  continuously, 
and  with  the  exception  of  the  New  York  Meteorological  Observ- 
atory in  Central  Park,  the  writer  believes  this  Observatory  to 
be  the  best  equipped  in  the  United  States.  The  instrumental 
outfit  is  now  as  follows  : 

Barometers.  These  are  kept  in  the  lower  room  of  the  tower, 
where  the  temperature  is  most  uniform.  The  Observatory 
standard  is  a  Hicks  Fortin  barometer,  reading  to  .002  inch. 
Although  verified  at  Kew  Observatory,  its  corrected  readings, 


tf  THE    BLUE    HILL 

as  determined  indirectly,  differ  by  — .013  inch  from  the  Signal 
Office  standards  at  Washington.  A  smaller  Green  barometer, 
which  reads  also  to  .002  inch,  has  been  compared  with  those  of 
the  Signal  Service  at  Washington  and  Boston.  In  reducing  the 
pressure  to  sea-level,  instead  of  applying  a  monthly  constant, 
as  was  the  practice  of  the  Signal  Service,  the  correction  at  Blue 
Hill  is  obtained  from  a  table  based  on  Laplace's  formula,  calcu- 
lated for  a  height  of  six  hundred  and  forty  feet,  in  which  the 
temperature  of  the  external  air  at  the  time  of  observation  is 
one  factor.  The  correction  to  reduce  to  the  standard  gravity 
of  latitude  45°,  is  the  same  as  that  used  by  the  Boston  office, 
as  are  the  temperature  correction  tables.  A  Draper  barograph, 
multiplying  three  times  and  giving  a  continuous  record,  has 
been  in  operation  since  May,  1885.  Commencing  in  July, 
1885,  the  record  has  been  checked  by  daily  comparisons  with 
the  standard  barometer,  and  the  barograph  is  now  so  well  regu- 
lated that  the  correction  is  usually  less  than  .01  inch.  A  Rich- 
ard aneroid  barograph  is  kept  ready  as  a  reserve  instrument. 

Thermometers,  Hygrometers,  etc.  The  thermometers  have 
all  been  verified,  and  the  Observatory  has  Hicks  thermometers 
with  Kew  certificates,  and  others  made  by  Baudin  of  Paris,  as 
standards.  From  the  north  side  of  the  tower,  fifteen  feet 
above  the  ground,  is  built  a  window  shelter,  in  the  construction 
of  which  special  pains  were  taken  to  secure  ventilation  by  mak- 
ing the  roof  double  and  by  setting  the  shelter  six  inches  out 
from  the  wall,  and  to  prevent  radiation  by  having  double  win- 
dows. An  isolated  shelter,  built  according  to  Prof.  H.  A. 
Hazen's  specifications,  shows  seldom  a  difference  of  1°,  except 
during  rapid  changes  of  temperature,  when  the  wall  shelter 
is  somewhat  sluggish.  For  convenience,  therefore,  the  Green 
wet  and  dry  bulb  and  maximum  and  minimum  thermometers, 
together  with  the  Richard  thermograph  and  registering  hygrom- 
eter, are  kept  in  the  window  shelter.  The  error  of  the  Richard 
thermograph,  ascertained  daily  by  readings  with  the  thermom- 
eters, is  ordinarily  less  than  1°.  A  Draper  metallic  thermo-' 
graph,  kept  at  the  base  station,  has  a  somewhat  larger  error. 
A  "  turnover  thermometer  "  of  Negretti  and  Zambra  can  be  set 
to  register  the  temperature  at  any  pre-determined  hour,  arid 


METEOROLOGICAL  OBSERVATORY.  9 

there  are  Hicks  solar  and  terrestrial  radiation  thermometers, 
which  have,  however,  not  yet  been  used.  A  Koppe  hair  hygrom- 
eter h;is  proved  to  be  the  best  method  of  determining  the  rela- 
tive humidity  in  cold  weather,  and  there  is  an  Alluard  conden- 
sation dew-point  apparatus  to  be  used  as  a  test.  The  tables  for 
calculating  the  dew-point  and  relative  humidity  are  those  calcu- 
lated for  a  pressure  of  thirty  inches  in  the  Instructions  for  Vol- 
untary Observers  of  the  /Signal  Service.  A  Richard  registering 
hygrometer  has  given  satisfactory  results  for  this  class  of  instru- 
ment. Its  readings  are  corrected  daily  by  comparisons  with 
the  psychrometer  or  hygrometer.  Browning  and  Hilger  rain- 
band  spectroscopes  have  been  employed  to  determine  the 
humidity  of  the  upper  atmosphere. 

Anemoscope  and  Anemometers.  These  are  exposed  eleven 
feet  above  the  roof  of  the  tower  and  thirty-five  feet  above  the 
ground.  A  Draper  anemoscope  and  anemometer,  recording 
mechanically  the  \lirection  and  velocity  of  the  wind,  have  given 
continuous  records  since  March,  1885,  with  the  exception  of 
short  periods  during  which  repairs  were  necessary.  Together 
-with  the  other  Draper  instruments,  they  were  made  for  the 
Observatory  by  Black  &  Pfister  of  New  York.  A  Hahl 
anemometer  of  the  Signal  Service  pattern,  recording  electrically 
each  mile  of  wind  by  means  of  the  Gibbon  self-register,  has 
been  in  operation  during  1886,  and  serves  to  show  brief  gusts 
and  to  supply  breaks  in  the  Draper  record.  These  instruments 
agree  tolerably  well  together,  and  with  a  Hicks  hand  anemom- 
eter, graduated  at  Kew,  and  of  a  pattern  adopted  by  the  Eng- 
lish Meteorological  Office.  A  pressure  gauge,  constructed  for 
the  writer,  presents  a  disk  with  a  square  foot  of  surface  normal 
to  the  wind  by  means  of  a  vane.  Pressure  upon  the  plate 
stretches  a  spring  and  leaves  an  index  at  the  maximum  pressure 
in  pounds  to  which  it  has  been  subjected  in  the  course  of  the 
day.  The  agreement  of  this  gauge  with  the  anemometer,  after 
the  equivalent  velocity  is  deduced  from  the  pressure,  is  remark- 
able, as  the  figures  given  in  the  next  chapter  show.  Another 
pressure  gauge,  with  a  rack  and  pawl  to  hold  the  plate  in  the 
position  corresponding  to  the  maximum  pressure,  designed  to 
obviate  the  error  which  might  be  caused  by  the  momentum  of 
the  plate  in  the  preceding  gauge,  has  not  proved  satisfactory. 


10  THE    BLUE    HILL, 

I?ain  and  Snow  Gauges.  The  standard  rain  gauge  is  that 
devised  by  the  New  England  Meteorological  Society.  It  is 
eight  inches  in  diameter,  and  the  water  is  poured  into  a  tube 
multiplying  ten  times  and  measured  with  a  stick.  A  snow 
gauge  with  the  same  receiving  surface  as  the  above  but  enlarged 
below  to  prevent  the  snow  from  blowing  out,  was  used  last 
winter  with  success.  To  prevent  loss  in  melting  the  snow  for 
measurement,  this  gauge  is  weighed  on  a  spring  balance  gradu- 
ated to  inches  and  hundredth;*  and  compensated  for  the  weight 
of  the  empty  gauge.  Weighing  is  now  the  method  used  for  rain, 
as  the  amount  which  has  fallen  can  thus  be  quickly  ascertained 
at  any  time  during  a  storm  without  emptying  the  gauge.  A 
rain  gauge,  recording  the  time  of  occurrence,  the  rate  and  amount 
of  the  rainfall,  made  by  Richard  Brothers  of  Paris,  on  the  weigh- 
ing principle,  after  the  writer's  design,  has  been  in  use  since 
March,  1886,  and  gives  fairly  good  results*  A  satisfactory 
gauge  for  recording  snow  is  yet  to  be  devised,  and  the  writer  is 
working  on  the  problem. 

Sunshine  and  Cloud  Instruments  and  Tests  of  Visibility. 
A  Campbell-Stokes  sunshine  recorder  registers  by  burning  a 
card  the  hours  of  bright  sunshine,  while  a  Jordan  instrument 
registers  both  bright  and  faint  sunshine  photographically.  The 
former,  which  is  the  standard  instrument  the  world  over,  has 
been  in  use  since  December,  1885.  From  the  percentage  of 
possible  sunshine,  the  mean  cloudiness  is  obtained,  it  having 
been  found  that  the  mean  cloudiness  thus  determined  differs 
but  slightly  from  that  calculated  from  three  daily  "  eye  "  observa- 
tions. A  cloud  mirror,  in  which  the  altitude  and  azimuth  of 
clouds  can  be  measured,  was  made  by  Mr.  Lowe  of  Boston,  for 
Mr.  Clayton,  the  present  observer,  and  some  measurements  of 
the  velocity  and  height  of  clouds  have  been  made  by  him.  The 
velocity  with  which  the  clouds  move  is  found  by  noting  the 
time  which  their  shadows  require  to  traverse  known  distances 
on  the  plain  below.  Only  clouds  of  the  stratus  and  cumulus 
type  give  shadows  which  can  be  thus  used.  The  velocity  of 
a  cloud  being  known,  two  angular  measurements  from  the  same 
point,  at  a  definite  interval  of  time  apart,  enable  its  height  to 
be  calculated.  Particular  attention  has,  of  late,  been  given  to 


METEOROLOGICAL  OBSERVATORY.  11 

the  direction  of  motion  of  clouds,  particularly  those  of  the 
cirrus  type.  A  record  of  visibility  of  the  mountains  situated 
at  different  distances  is  kept,  and  the  clearness  which  is  .said 
to  precede  storms  is  found  to  have  significance  under  certain 
conditions  of  pressure.  A  4-inch  telescope,  made  by  Clacey  of 
Cambridgeport,  though  not  strictly  a  meteorological  instrument, 
may  be  mentioned. 

In  order  to  insure  continuity  of  records  in  case  of  a  break- 
down, the  instruments  are  mostly  in  duplicate,  and  when  the 
whole  instrument  cannot  be  duplicated,  spare  pieces,  such  as 
clocks,  are  kept  on  hand.  The  wind  instruments  are  especially 
liable  to  accident,  and  when  it  is  considered  how  they  are  strained 
by  violent  gales,  and  that  some  13,000  miles  of  wind  pass  over 
them  each  month,  the  necessity  for  good  workmanship  in  their 
construction,  and  careful  attention  to  their  action  is  apparent. 
The  Observatory  was,  necessarily  at  first,  and  is  still  to  some 
extent,  an  experimental  station  where  new  instruments  are  tested 
and  modified  as  experience  may  suggest. 

THE  WORK  OF  THE  OBSERVATORY. 

Tri-daily  "eye"  observations  at  7  A.  M.,  3  and  11  r.  M., 
synchronous  with  and  similar  to  those  of  the  Signal  Service, 
were  begun  Feb.  1,  1885,  and  continued  until  April  1,  1886, 
without  an  omission.  In  one  case,  only,  was  an  observation 
taken  an  hour  late.  A  summary  of  these  observations  for  the 
year  ending  Jan.  31,  1886,  together  with  the  summary  of  the 
corresponding  observations  made  at  the  Boston  Signal  Service 
station,  ten  and  a  half  miles  north  of  and  five  hundred  and 
fifteen  feet  below  the  Observatory,  has  been  printed  and  sent  to 
the  weather  services  of  this  country  and  Europe  and  to  persons 
interested. 

This  summary  shows  the  mean  pressure  for  the  year,  reduced 
to  sea-level,  to  have  diifered  but  .002  inch  at  the  two  stations. 
The  mean  annual  temperature  was  44.4°,  or  2.7°  degrees  lower 
than  at  Boston,  giving  a  decrease  of  one  degree  for  each  one 
hundred  and  ninety-one  feet  of  elevation,  which  is  a  much  more 
rapid  decrease  than  the  normal ;  but  it  may  be  explained  by  the 
fact  that  the  temperature  of  a  city  is  abnormally  higher  than  at 


12  THE    BLUE    HILL 

the  same  elevation  in  the  country.  The  difference  was  least 
(1.1°)  in  May,  due  to  the  cooling  influence  of  the  east  winds 
which  prevailed  in  Boston,  and  greatest  (4.0°)  in  February, 
when  the  city  was  most  heated  artificially.  The  extremes  of 
temperature  on  Blue  Hill  were  91.2°  and — 15.0°,  or  1.6°  and 
4. 9°  lower,  respectively,  than  the  correspon< ling  temperatures  at 
Boston.  The  mean  relative  humidity  (73.7  per  cent)  was  4 
per  cent  higher  on  the  Hill  than  in  the  city,  though  the  very 
low  humidities  of  13  and  14  per  cent  were  recorded.  The 
total  precipitation  (39.00  inches),  instead  of  being  greater,  as 
is  usual  at  high  stations,  was  7.85  inches  less  than  in  Boston  ; 
but,  since  the  deficiency  was  greatest  in  the  winter,  this  may  be 
partly  due  to  the  blowing  of  the  snow  out  of  the  gauire,  at  that 
time  used,  by  the  high  winds  on  Blue  Hill.  But  the  greatest 
discordance  is  in  the  wind  records,  which  show  how  much  the 
wind  is  influenced  by  friction  with  the  earth's  surface.  The  total 
wind  movement  for  the  year  was  63  per  cent  greater  than  at  Bos- 
ton, though  the  anemometer  there  is  on  a  high  building.  Blue 
Hill,  in  fact,  is  one  of  the  most  windy  stations  at  which  observa- 
tions are  made  in  the  United  States,  the  total  movement  of  the 
wind  for  the  year  ending  with  January,  1886,  for  B  ue  Hill  and 
the  four  most  windy  Signal  Service  stations  being  as  follows  : 
Mt.  Washington,  N.  H.,  275,244  miles  ;  Pike's  Peak,  Col.,  173,- 
859  miles;  Cape  Mendocino,  Cal.  (11  months),  160,226  miles; 
Blue  Hill,  Mass,  (insufficient)  ,166,1 10  milos  ;  Sandy  Hook,  N.  J. , 
142,696  miles.  The  average  hourly  velocity  on  Blue  Hill  was, 
therefore,  18.9  miles  per  hour,  as  against  11.7  miles  at  Boston. 
The  greatest  number  of  miles  in  one  hour  was  74 ;  the  highest 
wind  in  Boston  having  blown  at  the  rate  of  64  miles  per  hour 
for  fifteen  minutes.  Calms  on  the  Hill  are  very  rare.  The 
direction  of  the  wind  frequently  varies  considerably  from  that 
at  Boston,  though  the  prevailing  wind  for  the  year  at  both  sta- 
tions was  west. 

Normal  values  of  the  chief  elements  for  Blue  Hill  have  been 
computed  by  comparing  the  first  year's  observations  with  the 
corresponding  observations  of  the  Signal  Service  at  Boston, 
whose  deviations  from  a  mean  of  fifteen  years  were  known  and 
assumed  to  be  the  same  as  for  Blue  Hill.  On  account  of  the 


METEOROLOGICAL  OBSERVATORY. 


13 


uncertainity  of  the  precipitation  record  on  Blue  Hill  for  the  first 
year,  the  normal  precipitation  there  has  been  provisionally  as- 
sumed to  he  the  &ame  as  for  Boston.  The  monthly  and  annual 
normals  are  given  in  this  table  : 

NORMALS   OF  THE   BLUE   HILL   OBSERVATOKY. 


MONTH  AND  TEAR. 

PRESSURE 
REDUCED  TO  32° 
AND  SEA  LEVEL. 

TEMPERATURE 
IN 
DEGREES    PAHR. 

PRECIPITATION 
IN  INCHES. 

30  09 

227 

444 

30  10 

24  8 

3  81) 

March 

29  94 

30  4 

4  61 

April    

29  91 

41  9 

3  87 

May 

29  98 

55  2 

H  50 

99  95 

63  2 

3  51 

July 

29  91 

69  7 

3  64 

30  03 

66  7 

4  53 

- 

of)  KG 

59  9 

0   «(? 

30  12 

49  7 

4  28 

30  10 

36  3 

T;  jo 

30  05 

26  9 

3  51 

Year         ,                         

30  02 

45  6 

47  80 

Most  of  the  data  is  now  obtained  from  the  charts  of  the  self- 
recording  instruments,  whose  indications  are  checked  daily  by  an 
"eye"  observation  of  the  standard  instruments  at  11  P.  M.,  and 
occasionally  at  other  times.  The  corrected  figures  are  entered 
in  a  daily  "form."  A  monthly  summary,  compiled  from  this, 
and  manifolded  by  the  cyclostyle  process,  is  now  sent  to  some 
twenty  persons  interested,  besides  the  New  England  Meteoro- 
logical Society  and  the  United  States  Signal  Service,  whose 
special  "forms  "  are  also  filled  out.  Some  of  this  data  appears 
in  the  monthly  Bulletin  of  the  Society  and  the  Weather  Review 
of  the  Signal  Service.  The  records  of  the  Observatory  are  at 
the  service  of  any  one  who  wishes  to  make  use  of  them,  and 
copies  of  the  original  traces  have  been  occasionally  supplied. 
The  Observatory  receives  the  daily  record  of  the  observations 
of  the  Boston  Signal  station,  and  monthlyxreports  of  tempera- 
ture and  precipitation  from  Milton  and  Randolph.  Since  July, 
1886,  it  has  had  its  own  station,  provided  with  thermometers 
and  rain  gauge,  at  the  base  of  the  Hill,  which  is  visited  daily. 
This  station  is  situated  at  the  junction  of  Canton  and  Blue  Hill 


14  THE    BLUE    HILL 

Avenues,  in  Milton,  and  is  three  quarters  of  a  mile  northwest 
of  and  four  hundred  and  forty  feet  below  the  Observatory.  It 
would  be  premature  to  compare  the  records  of  the  base  and 
summit  stations,  but  the  fact  that  some  marked  inversions  of 
temperature  have  occurred,  amounting  in  one  case  to  twenty 
degrees,  should  be  mentioned.  The  conditions  which  accom- 
panied one  of  these  inversions  were  described  by  Mr.  Clayton 
in  Science,  Vol.  VIII.,  Nos.  188  and  190.  The  variation  of 
rainfall  between  the  two  stations  is  also  sometimes  remarkable, 
having  been  nearly  an  inch  in  a  single  storm. 

Thunder-storm  observations  made  on  the  Hill  for  the  New 
England  Meteorological  Society,  which  has  undertaken  to  inves- 
tigate the  subject  during  the  past  two  summers,  were  valuable, 
because  this  station  was  one  of  the  few  provided  with  self-record- 
ing instruments.  The  thunder-storms  are  generally  attended 
by  curious  oscillations  of  pressure,  which  have  elsewhere  been 
found  to  be  characteristic  of  thunder-storms,  and  their  occur- 
rence on  the  barograph  sheet  has  served  to  detect  storms  of  this 
class,  even  when  their  thunder  and  lightning  were  not  noted. 
Other  sharply  serrated  curves  on  the  barograph  sheet  during 
heavy  gales  have  been  well  maintained  by  Mr.  Clayton  in  a 
lively  discussion  in  Vols.  VII.  and  VIII.  of  Science  to  be 
due  to  gusts  of  wind.  Professor  Abbe  of  the  Army  Signal 
Office  has  suggested  experiments  be  made  here  on  this  subject, 
which  the  writer  has  agreed  to  carry  out. 

Perhaps  the  most  important  work  was  commenced  last  Feb- 
ruary in  the  tabulation  of  the  hourly  values  of  the  atmospheric 
pressure,  and  of  the  velocity  of  the  wind,  in  order  to  establish 
their  diurnal  periods  for  each  of  the  months.  Up  to  the  pres- 
ent time,  no  breaks  in  the  record  have  occurred,  and  the  tab- 
ulation and  reduction  have  been  kept  up  to  date,  the  laborious 
additions  being  facilitated  by  the  use  of  the  Colmar  Arithmom- 
eter. It  is  intended  to  publish  these  hourly  means,  with  the 
original  figures,  at  the  end  of  the  year,  and,  as  this  will  be 
almost  the  only  data  of  the  kind  published  for  this  country,  it 
will  be  valuable  to  meteorologists. 

The  following  experimental  work  has  been  done  :  — 

During  June,  1885,  Mr.  Alexander  McAdie  of  the   Signal 


METEOROLOGICAL   OBSERVATORY.  15 

Corps  made  some  experiments  at  the  Observatory  upon  atmos- 
pheric electricity,  using  a  kite  and  a  Trovvbridge  electrometer. 
An  account  of  these  experiments  was  communicated  to  the 
American  Academy  of  Arts  and  Sciences  in  June,  1885. 

A  series  of  comparisons  of  a  rain  gauge  placed  in  the  centre 
of  the  tower  roof,  24  feet  above  the  ground,  with  a  gauge  on 
the  ground,  made  during  the  spring  of  1885,  showed  an  increase 
of  56  per  cent  in  the  precipitation  caught  in  the  ground  gauge, 
which  was  almost  entirely  due  to  the  wind  eddies  on  the  tower. 
This  shows  that  a  rain  gauge  should  not  be  placed  on  a  roof  as 
is  done  at  many  of  the  Signal  Service  stations. 

A  series  of  comparisons  of  thermometers  exposed  in  the 
Hazen  shelter,  adopted  by  the  Signal  Service,  and  in  a  window 
shelter,  have  been  conducted  this  year.  Referring  the  read- 
ings of  the  thermometers  to  those  in  the  Hazen  shelter  as  a 
standard,  the  mean  error  for  the  window  shelter  was,  for  the 
dry  bulb  -j-0-40,  and  for  the  wet  bulb  -J-0.50,  during  February, 
but  only  -f~0.1°  and  -j-0.20,  respectively,  during  March.  Ex- 
treme differences  of  nearly  2°  have  occurred.  Maximum  and 
minimum  thermometers  exposed  in  these  shelters  showed  errors 
of  -f-0.50  for  the  maximum  and  +0.4°  for  the  minimum  during 
July,  and  pf — 0.2°  for  both  thermometers  during  August. 
These  differences  seem  to  be  influenced  by  the  direction  of  the 
wind ;  and,  as  they  are  small,  it  has  been  concluded  that  with 
such  a  strong  circulation  of  air  as  exists  on  Blue  Hill,  the  ex- 
posure of  thermometers  in  a  window  shelter  is  sufficiently  good. 

It  is  generally  supposed  that  .the  dew-point  and  relative 
humidity  of  the  air,  obtained  from  readings  of  the  wet  and  dry 
bulb  thermometer  in  cold  weather,  are  not  to  be  depended  on. 
Some  experiments  on  this  subject  were  made  during  February 
and  March,  1886,  when  simultaneous  tri-daily  observations 
were  taken  of  the  Koppe  hair  hygrometer  and  of  the  wet  and 
dry  bulb  thermometers,  from  whose  readings  the  relative  humid- 
ity was  calculated.  The  mean  relative  humidity  for  February 
was  79  per  cent  by  the  psychrometer  and  73  per  cent  by  the 
hygrometer,  and  for  March  75  per  cent  by  the  psychrometer 
and  72  per  cent  by  the  hygrometer ;  which  shows  that  when 
properly  manipulated  the  psychrometer  gives  fairly  good  results 


1(1 


THE    BLUE    HILL 


in  cold  weather,  assuming  from  the  following  experiments  that 
the  hygrometer  is  reliable.  The  relative  humidities  obtained  by 
the  two  methods  during  July,  1886,  gave  a  mean  of  59  percent 
and  58  per  cent,  respectively,  for  the  3  p.  M.  observation,  and 
both  gave  a  mean  of  82  per  cent  for  the  11  p.  M.  observation. 
As  the  psychrometer  is  trustworthy  in  warm  weather,  these 
experiments  prove  that  the  hair  hygrometer,  or,  at  least,  the 
Koppe  form  of  it,  is  a  very  good  instrument  for  determining  the 
relative  humidity  at  all  seasons. 

On  account  of  the  unusual  advantages  which  the  Observatory 
offers  for  the  study  of  the  relation  of  wind  pressure  and  velocity, 
its  investigation  has  been  undertaken  this  year,  using  the  Hahl 
anemometer  and  the  pressure  gauge  situated  on  the  tower. 
Some  of  the  results  of  these  experiments  are  given  in  the  fol- 
lowing table.  The  velocity  corresponding  to  the  recorded  pres- 
sure is  obtained  from  the  table  computed  by  Colonel  James,  who 
assumed  that  the  square  of  the  velocity  in  miles  per  hour,  mul- 
tiplied by  .005,  gave  the  pressure  in  pounds  per  square  foot. 

RELATION  OF  THE  PRESSURE  TO  THE  VELOCITY  OF  THE  WIND. 


Pressure  per  Square 
Foot,  in  Ibs. 

Equivalent  Velocity,  in 
Miles  per  11  our. 

Highest  Mean  Velocity 
for  Five  Minutes,  in 
Miles  per  Hour. 

Number  of 
Experiments  Quoted. 

20 

20 

22 

3 

4.0 

28 

28 

3 

6.0 

35 

35 

3 

8.0 

40 

38 

3 

10.0 

45 

40 

2 

12.0 

49 

45 

3 

15.0 

55 

55 

2 

17.0 

58 

56 

8 

21.5 

66 

65 

240 

69 

64 

25.5 

71 

66 

26.0 

72 

70 

26.5 

78 

66 

31.0 

7!) 

75 

32.5 

81 

72 

36.5 

85 

84 

43.7 

93 

84 

The  Blue  Hill  experiments  seem  to  show  that  this  formula 
gives  a  close  approximation  to  the  relation  betvveen  pressure  and 
velocity.  The  extreme  velocity  of  the  gusts  would  naturally 


METEOROLOGICAL    OBSERVATORY.  17 

be  expected  to  exceed  the  mean  velocity  for  five  minutes  as 
shown  by  the  anemometer,  and  this  is  generally  found  to  be  the 
case.  It  will  be  noticed  that  the  agreement  is  closest  at  moder- 
ate velocities,  but  whether  this  is  due  to  the  inertia  of  the  pres- 
sure plate,  causing  it  to  lag  with  light  winds,  or  whether  the 
velocity  of  the  gusts  exceeds  in  a  greater  ratio  the  mean 
velocity  during  high  winds  than  during  low  ones  cannot  now 
be  stated. 

Experiments  were  conducted  for  nine  months  during  1885-86, 
with  the  rain-band  spectroscope,  to  test  its  efficiency  to  foretell 
rain.  Its  use  has  been  recommended  in  England  by  Smyth, 
Mill,  Cory,  and  others,  but  the  results  obtained  at  Blue  Hill 
do  not  confirm  their  conclusions.  The  observations  were  first 
made  with  a  Browning  and  afterwards  with  a  Hilger  instru- 
ment, at  7  A.  M.  and  3  P.  M.,  and  the  rainfall  in  the  following 
eight  hours  noted.  A  possible  ten  being  taken  as  the  sum  of 
the  maximum  intensity  of  two  readings  at  the  horizon  and  at 
an  angle  of  45  &,  five  was  considered  as  a  sign  of  rain.  The 
average  success  of  predictions  made  for  eight  hours  in  advance 
from  the  spectroscope  alone,  for  the  warm  months  of  July, 
August,  and  September,  was  eighty-five  per  cent  for  the  morn- 
ing and  eighty  per  cent  for  the  afternoon  observation ;  for  the 
cool  months  of  October  and  November,  eighty-one  per  cent 
for  the  morning  and  eighty-seven  per  cent  for  the  afternoon 
observation ;  and  for  the  cold  months  of  December,  January, 
February,  and  March,  seventy-five  per  cent  for  the  morning 
and  eighty-one  per  cent  for  the  afternoon  observation.  A  higher 
degree  of  success  in  rain  predictions  for  eight  hours  in  advance 
could  probably  be  attained  by  simple  observations  of  the  wind 
and  clouds. 

The  display  of  weather  signals  has  become  such  an  important 
part  of  the  work  of  the  Observatory,  that  an  account  of  the 
development  of  this  branch  is  given  in  a  special  chapter. 

This  comprises  an  outline  of  the  work  of  the  Observatory  up 
to  the  present  time.  As  to  the  future,  little  can  be  said.  Since 
the  Observatory  is  a  private  enterprise,  its  maintenance  is  less 
assured  than  if  managed  by  a  corporation  or  by  the  Govern- 
ment. It  is  thus  a  creature  of  circumstance,  but,  should  it 


18  THE   BLUE    HILL 

/ 

now  cease  to  exist,  many  of  the  objects  for  which  it  was  estab- 
lished will  have  been  accomplished,  and  the  data  already  ob- 
tained will  furnish  abundant  material  for  future  study. 

WEATHER   SIGNALS. 

One  of  the  first  efforts,  after  the  establishment  of  the  Observ- 
atory, was  to  utilize  its  conspicuous  situation  to  disseminate 
the  weather  predictions  over  the  surrounding  country.  Ac- 
cordingly, an  order  having  been  obtained  from  the  Chief  Signal 
Officer  authorizing  the  observer  at  Boston  to  transmit  the 
orders  relating  to  the  cold  wave  signal,  the  following  circular 
was  sent  to  twenty  post-offices  and  twenty-six  railroad  stations 
within  a  five-mile  radius  of  the  Hill,  from  whose  neighborhood 
the  flag  on  the  Observatory  could  be  seen  : 

To  the  Postmaster  at 

PLEASE  POST   IN   A   CONSPICUOUS   PLACE. 

COLD  WAVE  FLAG. 


In  co-operation  with  the  United  States  Signal  Service  and  the  New  Eng- 
land Meteorological  Society,  a  Cold  Wave  Flag  (white  with  a  black  centre) 
will  be  displayed  henceforth  from  the  summit  of  Great  Blue  Hill,  Milton,  as  a 
warning  of  the  approach  of  decidedly  colder  weather. 

A.  LAWRENCE  ROTCH, 

Proprietor  of  the 

BLUE  HILL  METEOROLOGICAL  OBSERVATORY. 
FKB.  1,  1885. 

The  displays  have  been  continued  up  to  the  present  time,  the 
flag  being  ordered  up  by  telephone  from  Boston,  on  receipt  of 
the  telegraphic  order  from  Washington.  Out  of  twenty-eight 
displays  to  April  1, 1886,  twenty-two,  or  seventy-nine  per  cent, 
were  considered  verified.  The  verification,  as  estimated  at  the 
Boston  Signal  station,  is  larger. 

Besides  the  cold  wave  warnings,  it  was  decided  to  attempt 
the  local  prediction  of  rain,  as  the  most  important  weather  ele- 
ment, in  order  to  give  an  added  interest  to  the  study  of  storm 
movements.  Accordingly  the  fallowing  circular  was  issued  : 


METEOROLOGICAL    OBSERVATORY.  19 

PLEASE  POST  IN   A   CONSPICUOUS   PLACE. 

RAIN   WARNINGS, 


Beginning  May  1,  1885,  the  Blue  Hill  Meteorological  Observatory  will  at- 
tempt to  give  warning  of  rain. 

A  square  Red  Flag  displayed  during  the  day  and  a  Red  Lauteru  shown  by 
uight,  at  the  Observatory  on  Blue  Hill,  will  indicate  that  Rain  is  expected  iu 
the  vicinity  within  Twelve  Hours  from  the  first  display  of  these  signals. 

The  display  of  the  Black  and  White  Cold  Wave  Flag,  as  ordered  by  the 
United  States  Signal  Service,  will  be  continued. 

As  the  Rain  Warnings  are  an  experiment  of  the  undersigned,  they  will  be 
discontinued  if  unsuccessful. 

A.   LAWRENCE  RO TCH, 

BLUE  HILL  METEOROLOGICAL  OBSERVATORY, 

READVILLE  P.  OM  MASS. 

In  making  these  predictions  all  available  data  was  used,  in- 
cluding the  Signal  Service  reports  furnished  through  the  cour- 
tesy of  the  Boston  observer,  Sergeant  O.  B.  Cole.  During 
May,  the  rain  signal  was  displayed  eleven  times,  and  of  these 
displays,  eight,  or  seventy-three  per  cent,  were  followed  by  rain 
within  an  average  time  of  six  hours.  The  Signal  Service  ruin 
indications  for  New  England  for  twenty-four  hours,  tested  for 
Blue  Hill,  gave  a  verification  of  fifty-one  per  cent.  During 
June,  owing  to  the  numerous  local  showers,  the  success  of  the 
Observatory  and  Signal  Service  rain  predictions  was  only  about 
forty-tvvd  per  cent.  Partly  on  this  account,  and  partly  on  ac- 
count of  the  watchfulness  necessary  to  continue  these  predic- 
tions made  at  any  hour,  the  Council  of  the  New  England  Mete- 
orological Society,  on  taking  charge  of  the  Observatory,  July 
1,  1885,  sent  out  this  circular: 

PLEASE    POST  IN  A  CONSPICUOUS  PLACE. 

RAIN    WARNINGS. 


Until  further  notice,  the  Rain  Signal  on  Blue  Hill  will  consist  of  a  Red 
Flag  by  day,  which  will  be  displayed  in  accordance  with  the  weather  indica- 
tions issued  by  the  United  States  Signal  Service  for  New  England, 

NEW   ENGLAND    METEOROLOGICAL    SOCIETY, 

In  charge,  of 

BLUE  HILL  METEOROLOGICAL  OBSKRVATOKY. 
JULY  1,  1885. 


20 


THE    BLUE    HILL 


From  the  important  requisite  of  visibility  at  a  distance,  none 
of  the  weather  flags,  with  red  and  blue  suns,  moons  and  stars, 
which  had  been  introduced  by  the  Society,  were  possible  on 
Blue  Hill,  and  the  red  flag  was,  therefore,  retained  to  indicate 
rain.  The  practice  followed  was  to  display  the  flag  when  the 
midnight  indications  of  the  Signal  Service  for  New  England, 
received  by  telephone  at  7.30  A.  M.,  warranted  it;  but  to  have 
the  flag  also  governed  by  the  10  A.  M.  indications,  received  at  the 
Observatory  about  noon,  and  in  all  cases  to  lower  the  flag  at 
sunset.  These  warnings  were  continued  during  the  summer 
and  autumn,  and  the  per  cent  of  verification  of  each  set  of  pre- 
dictions, considering  the  weather  at  Blue  Hill  as  either  fair  or 
rainy,  was  as  follows  : 


MONTH. 

TWENTY-FOUK  HOUHS,  FROM 
7  A.  M.                               3  P.  M. 

Ju]y                                       .                  

65 

45 
80 
64 

71 
61 
80 
77 

A  modification  of  the  method  was  commenced  in  November, 
by  which  the  flag  was  hoisted  after  the  receipt,  at  7.30  A.  M.,  of 
the  special  predictions  made  by  the  Signal  Service  for  the 
Meteorological  Society,  whenever  the  flags  numbered  4  or  6 
of  its  code  were  specified.  The  percentage  of  verification  of 
each  day's  predictions  for  the  weather  of  the  twenty-four  hours 
commencing  at  7  A.  M.,  was  as  under  : 

November,  1885,  77;  December,  84;  January,  1886,  74; 
February,  83;  March,  81  ;  April,  66. 

Better  local  predictions  were  made  possible  after  May  1, 
1886,  by  the  charting  of  a  daily  weather  map  in  Boston,  show- 
ing the  weather  conditions  existing  over  the  United  States  at  7 
A.  M.,  75th  meridian  time.  Hitherto  such  a  map  had  been  litho- 
graphed only  in  Washington,  and  as  it  is  received  here  thirty-six 


METEOROLOGICAL   OBSERVATORY.  21 

hours  after  the  observations  on  which  it  is  based  are  made,  it  is 
useless  for  predicting  purposes.  The  issue  of  this  map  in  Boston 
was  brought  about  by  Sergeant  Cole,  who  got  permission  from 
the  Chief  Signal  Officer  to  chart  the  telegraphic  reports,  which 
have  always  been  received  in  Boston,  and  to  manifold  this  chart 
by  a  cyclostyle  apparatus  furnished  by  the  writer.  It  is  thus 
printed  within  four  hours  after  the  observations  are  made,  and 
at;  once  distributed  through  the  mail.  This  map  proved  so 
satisfactory  in  Boston  that  the  morning  tabular  bulletin  has 
been  discontinued  at  certain  central  stations,  and  the  map  sub- 
stituted. It  is  now  received  at  the  Observatory  about  2  p.  M., 
Sundays  included,  being  taken  to  and  from  the  trains  by  mes- 
sengers. 

Local  predictions  were  accordingly  resumed  at  the  Observa- 
tory May  1,  1886,  just  a  year  after  the  first  attempt,  subject  to 
these  rules :  When  the  flag  was  hoisted,  rain  was  expected  to 
occur  within  twenty-four  hours.  If  at  the  end  of  that  time 
more  rain  was  expected,  the  flag  was  kept  up.  If  rain  fell  on 
any  afternoon  and  the  flag  was  not  displayed  before  noon,  it 
was  accounted  a  failure  to  predict  the  rain.  A  flag  displayed 
in  the  afternoon  indicated  rain  the  next  day.  The  verification 
At  Blue  Hill  of  the  weather  predictions  for  May,  those  of  the 
Signal  Service  being  made  for  Massachusetts  at  1  A.  M.,  and 
appplying  from  7  A.  M.  of  that  day  to  7  A.  M.  of  the  following 
day,  was  as  follows  : 

Blue  Hill,  81  per  cent. 

Signal  Service,  68  per  cent. 

During  June  a  modification  of  this  plan  of  display  was  adopted, 
which  required  the  flag  to  be  hoisted  between  7  and  8  A.  M.,  and 
to  apply  for  the  succeeding  twenty-four  hours.  The  comparison 
of  the  two  sets  of  predictions  was  as  under,  the  conditions  being 
now  practically  identical  as  regarded  the  public  : 

Blue  Hill,  90  per  cent. 

Signal  Service,  77  per  cent. 

Finally  a  definite  plan  was  announced  to  go  into  effect  July 
1,  through  this  circular: 


THE   BLUE   HILL 
PLEASE  POST   IN  A  CONSPICUOUS   PLACE. 


BLUE    HILL 
WEATHER    SIGNALS, 


The  following  Rules  will  govern  the  display  of  signals  at  the  Bine  Hill 
Meteorological  Observatory  on  and  after  July  1,  1886. 

I.  A  Bed  Flag  will  indicate,  a-  heretofore,  Probable  Rain  in  the  vicinity. 

II.  Two  Red  Flags,   one  above  the  other,  will  indicate  Possible  Rain. 
This  is  not  intended  as  a  rain  prediction,  but  simply  to  show  that  some  of  the 
conditions  are  favorable  for  rain, 

III.  The  absence  of  Red  Flags  wilt  indicate  that  no  rain  is  expected. 

IV.  The  prediction  will  be  made  before  sunset  to  indicate  the  weather 
expected   for  the  following  day,  and  will  extend  from  midnight  to  midnight. 
These  predictions  will  ba  revised  each  morning  at  eight  o'clock,  and  the  Sig- 
nals changed  if  necessary. 

V.  A  White  Flag  with  a  Black  Centre  (seldom  displayed  in  summer)  will 
indicate  an  apppoaching  Cold  Wave. 

These  predictions,  with  the  exception  of  the  last,  will  be  independent  of 
those  of  the  U.  S.  Signal  Service. 

A.  LAWRENCE  ROTCH, 
BLUE  HILL  METEOROLOGICAL  OBSERVATORY. 

It  was  decided  that  if  rain  occurred  with  the  two  flags,  the 
prediction  was  a  failure,  while  fair  weather  would  make  this 
display  a  success.  This  rule  was  intended  to  make  the  rain 
prediction  as  definite  as  possible.  The  midnight  indications  of 
the  Signal  Service  for  Massachusetts  continue  to  be  received  by 
telephone,  at  7.30  A.  M.,  at  the  Observatory,  and,  together  with 
the  local  weather  observations,  help  to  make  up  the  morning 
prediction.  The  afternoon  prediction  is  dependent  on  the 
morning  weather  map,  and  upon  the  local  weather  observations. 
The  comparison  of  the  Blue  Hill  weather  predictions,  with  those 
of  the  Signal  Service,  up  to  the  present  time,  is  as  follows : 


JULY. 

AUG. 

BEPT. 

OCT. 

NOV. 

Blue  Hill  Sunset  Predictions  for  24  hours 

84 

fel 

80 

78 

77 

Blue  Hill  8  A.  M.  Predictions  for  16  hours 

90 

84 

83 

90 

90 

.        Signal  Service  Midnight  Indications  for 

68 

71 

63 

81 

70 

PER   CENT  VERIFIED. 


METEOROLOGICAL  OBSERVATORY.  8 

It  should  be  stated  that  in  all  cases  each  set  of  predictions 
has  been  tested  at  Blue  Hill  in  a  precisely  similar  manner,  .01 
inch  or  more  of  rain  or  melted  snow  within  the  specified  time 
constituting  rain.  It  is  difficult  to  estimate  the  value  of  the 
Blue  Hill  weather  signals,  which  can  be  plainly  seen  by  trav- 
ellers on  the  Boston  &  Providence  and  New  York  &  New 
England  Railroads,  and  in  nine  towns  by  some  forty  thou- 
sand people,  who  are,  undoubtedly,  more  dependent  upon  the 
weather  in  their  daily  avocations  than  are  the  dwellers  in  cities. 
Inquiry  shows  that,  although  implicit  confidence  is  not  always 
placed  in  the  signals,  yet  that  farmers  and  others  at  least  keep 
their  weather  eye  open  when  a  flag  is  flying  on  Blue  Hill.  Mr. 
Clayton  has  the  charge  of  these  signals, 'and  to  him  their  success 
is  due.  Lest  these  predictions,  ostensibly  pro  bono  publico, 
be  regarded  suspiciously,  it  should  be  stated  that  by  attempt- 
ing such  predictions,  a  constant  interest  is  given  to  the  study 
of  the  development  and  progress  of  storms,  which  is  one  of  the 
legitimate  objects  of  the  Observatory. 

The  superiority  of  these  local  predictions  over  the  Washing- 
ton predictions  of  the  Signal  Service  lies  in  the  fact  that  it  is  im- 
possible for  predictions  made  at  one  central  station  to  take  into 
account  local  causes  which  may  influence  the  weather  at  any 
distant  place.  These  influences  each  meteorologist  learns  for 
his  own  locality ;  and,  when  his  observations  are  combined  with 
a  knowledge  of  the  weather  conditions  existing  that  day  over 
a  large  extent  of  country,  as  shown  by  a  synoptic  chart,  he  is 
better  able  to  predict  the  weather  for  his  locality  than  is  the 
Signal  Service,  which  must  generalize  its  predictions  for  large 
areas,  though  the  weather  probabilities  for  his  own  town  are 
what  each  inhabitant  thereof  wishes  to  know.  Another  advan- 
tage in  favor  of  local  predictions  is  the  celerity  with  which  they 
may  be  disseminated*,  Thus,  if  the  7  A.  M.  observation  of  the 
Signal  Service  shows  indications  of  rain  that  day,  notice  can- 
not be  given  to  the  public  before  afternoon ;  while  if  the  fact  is 
locally  signalled  from  the  predicting  station',  by  flags  or  other- 
wise, the  public  can  be  at  once  informed.  The  Signal  Service 
has  recently  attempted  to  overcome  this  difficulty,  by  having 
its  predictions  commence  seven  hours  after  they  are  issued,  but 
this  aiming  at  longer  range  naturally  impairs  their  accuracy. 


24  THE   BLUE    HILL 

The  data  at  the  service  of  the  Washington  office  for  making 
predictions  is,  of  course,  far  greater  than  that  available  at 
this  Observatory.  Instead  of  one  daily  synoptic  chart  of  the 
weather  over  the  United  States  and  Canada,  one  is  prepared  in 
Washington  each  eight  hours ;  and  this  map,  besides  containing 
reports  from  many  more  stations  than  does  the  map  charted  in 
Boston,  has  the  elements  separated,  with  the  changes  which  have 
occurred  in  each  dui  ing  the  preceding  eight  hours.  With  these 
facilities  at  hand,  it  seems  that  the  predictions  of  the  Signal  Ser- 
vice should  be  better.  The  obvious  reasons  for  the  shortcom- 
ing appear  to  be  the  haste  with  which  forecasts  for  so  many 
districts  must  be  drawn  up,  and  the  frequent  changes  made  in 
the  predicting  officer,  •which  prevent  a  systematic  study  of 
weather  types.  As  the  preceding  verifications  in  this  locality 
of  the  Signal  Service  indications  may  seem  exceptionally  small, 
it  can  be  stated  that  they  agree  substantially  with  the  percent- 
ages of  revised  verifications  for  New  England,  published  in  the 
official  3/o??^?y  Weather  Review;  though  the  verifications  of  the 
Signal  Service  indications,  made  at  certain  flag-display  stations, 
and  communicated  through  the  Boston  Signal  office  to  the  New 
England  Meteorological  Society,  for  publication  in  its.  monthly 
Bulletin,  are  evidently  carelessly  made,  and  show  a  considerably 
higher  success  than  do  the  official  estimates  before  mentioned. 
The  proper  method  of  verifying  weather  predictions  has  been 
much  discussed,  but  no  definite  plan  had  been  universally 
adopted,  so  that  predictions  tested  at  different  places  cannot  be 
compared,  unless  the  methods  used  are  rigidly  the  same. 

ANNALS   OF  THE  OBSERVATORY. 

The  Observatory  was  taken  possession  of  Jan.  31,  1885,  by 
the  writer  and  the  observer,  Mr.  Gerrish,  and  at  midnight  a 
discharge  of  rockets  announced  the  opening  of  the  highest 
meteorological  station  on  the  Atlantic  coast.  The  lower  room 
of  the  tower  and  the  adjoining  bedroom  only  could  be  occupied, 
and  for  the  first  two  days,  until  the  steward  arrived,  the  ob- 
servers did  their  own  cooking. 

The  month  of  February  was  one  of  the  coldest  months  ever 
known  in  this  region.  The  mean  temperature  on  the  Hill  was 


BLUE  HILL 

METEOROLOG-/C/IL 

OBSERVATORY. 


METEOROLOGICAL    OBSERVATORY.  25 

16.5°,  or  4°  lower  than  the  Signal  office  figures  for  Boston,  but 
the  high  winds  made  the  difference  seem  greater.  The  low- 
est temperature  was,  however,  only  — 3.2°,  or  4°  lower  than  the 
Boston  minimum.  This  cold  was]  unpleasant  to  the  occupants 
of  the  unfinished  building,  which  double  windows  afterwards 
rendered  more  comfortable.  On  Feb.  16  occurred  a  gale 
which  has  hardly  been  equalled  since,  and  which  served  to  test 
the  stability  of  the  building.  Both  anemometers  were  blown 
away,  so  that  the  highest  velocity  of  the  wind  is  unknown  ;  but 
before  the  accident  occurred,  74  miles  per  hour  were  regis- 
tered, and  the  observer  thinks  that  for  five  minutes  the  velocity 
was  90  miles  per  hour.  The  cups  of  the  Ha  hi  anemometer 
were  again  blown  off  in  December  by  much  less  wind.  There 
was  little  snow  during  the  winter,  though  the  cold  weather 
continued  through  March.  The  spring  was  pleasant,  and  from 
this  time  forth  crowds  of  people  visited  the  Hill  at  all  hours  of 
the  day  and  night.  A  newspaper  complaint,  entitled  "  Is  it  a 
Monopoly  of  the  Blue  Hill  view?"  elicited  a  card  from  the 
writer,  in  which  he  stated  that  while  the  top  of  the  Hill,  as 
heretofore,  would  continue  to  be  open  to  the  public,  subject 
only  to  the  restriction  that  visitors  should  disturb  neither  the 
Observatory  nor  the  instruments  outside,  yet  that,  as  the  grounds 
were  private  property,  no  injustice  was  done  when  disorderly 
or  objectionable  people  were  ordered  from  the  premises.  The 
road,  which  had  been  badly  washed,  was  repaired  so  that  it 
was  again  practicable  for  carriages.  The  parapet  around  the 
tower  was  now  completed,  and  the  stone-work  pointed. 

On  account  of  the  absence  of  the  writer  in  Europe,  the  Coun- 
cil of  the  New  England  Meteorological  Society  kindly  assumed 
charge  of  the  Observatory  during  the  summer,  Mr.  Gerrish 
remaining  as  observer,  and  conducting  thunder-storm  observa- 
tions for  the  Society.  Some  of  these  storms  were  severe,  the 
squall  of  July  21  being  described  as  terrific.  Owing  to  its 
short  duration,  the  velocity  of  the  wind  could  not  be  ascertained 
from  the  anemograph  then  in  use,  but  an  idea  of  its  force  may 
be  had  from  the  fact  that  a  heavy  dog-kennel  was  carried  several 
hundred  feet  down  the  Hill  and  smashed  to  fragments,  and  stones 
hurled  against  the  building  with  sufficient  force  to  indent  the 


26  THE    BLUE    HILL 

wood.  The  thunder-storms,  however,  generally  moved  around 
the  Hill,  but  occasionally  lightning  played  about  the  building, 
which,  on  account  of  insufficient  ground  connection,  is  not  pro- 
vided with  conductors.  The  highest  temperature  during  the 
summer  was  1.6°  lower  than  at  Boston,  but  the  continual 
breeze  made  the  heat  seem  much  less.  The  spring  on  the  road- 
side having  dried  up,  water  for  drinking  was  brought  from  the 
base,  the  cistern  proving  sufficient  for  cooking  and  washing. 
The  Hill  was  occupied  in  June,  and  at  various  times  since,  by 
surveyors  of  the  United  States  Geological  and  State  Topo- 
graphical Surveys,  and  a  signal  was  erected  by  the  latter  over 
the  Coast  Survey  bolt. 

The  autumn,  which  was  cool  and  pleasant,  passed  unevent- 
fully, and  the  writer  resumed  charge  of  the  Observatory  in 
October.  The  permanent  snow  of  the  winter  came  very  late, 
and,  in  consequence,  the  supply  of  coal  which  was  to  be  replen- 
ished by  sled,  ran  low.  The  upper  part  of  the  road  became 
covered  with  ice,  so  that  the  coal  could  be  brought  but  half-way 
up  the  Hill.  On  Jan.  9  occurred  a  heavy  snow-storm.  The 
following  extract  from  the  Journal  of  this  period  reads  like  an 
arctic  experience  : 

Jan.  9.  "At  sunrise  a  snow-drift,  two  feet  deep,  was  found  in  the  hall- 
way, having  been  forced  in  through  the  cracks  of  the  doors  and  windows 
by  the  high  wind.  There  is  little  snow  on  the  Hill,  but  below  the  roads 
are  reported  to  be  blocked." 

Jan.  11.  "  The  observer  and  the  steward  went  to  the  base  and  brought 
up  a  large  basket  of  provisions  hung  on  a  pole  between  them.  The 
ascent  (usually  made  in  twenty  minutes)  occupied  an  hour.  At  noon,  as 
the  last  coal  was  burning  low,  a  rude  sled  was  constructed,  with  a  view 
of  attempting  to  drag  up  a  load  from  the  pile  on  the  roadside.  At  this 
juncture  the  teamster,  who  had  been  sent  for  the  day  before,  succeeded 
in  breaking  through  the  drifts  and  reaching  the  summit  with  some  of  the 
coal  which  was  distributed  along  the  road." 

The  fall  of  the  barometer  in  this  storm  was  very  great, 
amounting  to  over  one  inch  in  fifteen  hours.  The  barograph 
sheet  has  been  reproduced  in  the  December  number  of  the 
American  Meteorological  Journal  by  Prof.  Upton  in  a  discussion 
of  this  cyclone,  whose  centre  seems  to  have  passed  over  Blue  Hill. 
It  was  followed  within  a  week  by  an  anti-cyclone  which  sent  the 


METEOROLOGICAL  OBSERVATORY.  27 

barometer  (reduced  to  sea  level)  from  28.67  inches  up  to  30.85 
inches,  and  the  thermometer  down  to  — 15°,  the  highest  and  low- 
est pressures  and  the  lowest  temperature  on  record.  The  ice- 
storm  which  occurred  the  last  of  January  was  a  transformation 
to  fairyland.  The  trees,  building,  and  in  fact  every  object  was 
incrusted  with  ice  crystals,  the  anemometers  and  vane  being  so 
incasqd  as  to  be  rendered  useless.  The  weight  of  a  small 
branch  was  increased  forty-five  times  by  the  rain  and  fog  which 
froze  on  it  and  many  trees  were  thus  broken,  while  the  tele- 
phone wire  had  a  girth  of  eight  inches.  During  this  period, 
genuine  frostwork,  which  had  once  before  been  observed  on  the 
Hill,  attained  a  length  of  one  or  two  inches. 

Mr.  Gerrish  was  succeeded  by  Mr.  H.  Helm  Clayton  as  ob- 
server, on  Feb.  1,  and  some  new  investigations  were  then 
undertaken.  The  flood  in  the  Neponset  Valley  in  February 
was  an  interesting  sight  from  the  Hill.  The  Canton  meadows 
were  a  lake  filled  with  floating  cakes  of  ice,  through  which, 
for  several  days,  the  trains  on  the  Providence  Railroad 
could  be  seen  creeping  like  snails,  with  the  water  up  to  the  car 
steps.  Communication  with  Readville  by  road  was  during  this 
time  interrupted.  The  rainfall  which  caused  the  flood  was  here 
six  inches  in  fifty  hours,  but  this  was  increased  at  least  two 
inches  by  the  sudden  melting  of  the  ice  and  snow  on  the  ground. 
The  building  leaked  badly  then,  as  during  other  heavy  rains, 
the  water  being  driven  by  the  wind  through  the  pores  of  the 
stone.  During  the  last  days  of  February  occurred  the  violent 
northwest  gales,  which  are  probably  remembered  by  many. 
The  highest  velocity  of  the  wind  on  the  Hill  during  a  whole 
hour  was  seventy-three  miles,  on  the  28th,  and,  for  five 
minutes,  eighty-five  miles  per  hour.  The  highest  velocity  at 
Boston  during  fifteen  minutes  was  only  fifty-one  miles  an  hour. 
At  the  Observatory,  a  maximum  pressure  of  over  forty-three 
pounds  per  square  foot  was  recorded,  which  shows  the  velocity 
of  the  gusts  to  have  been  ninety-three  miles  an  hour.  The 
total  movement  of  the  wind  during  the  28th  was  1,467  miles, 
or  420  miles  more  than  any  previously  recorded  daily  move- 
ment. During  the  last  three  days  of  February,  3,735  miles  of 
wind  blew  over  the  Hill,  and  the  gale  continued  during  the  first 


28  THE    BLUE    HILL 

days  of  March  with  diminishing  force.  No  damage  resulted 
from  the  blow,  but  it  was  found  impossible  to  keep  the  build- 
ing warm,  the  observer  noting  that  water  froze  in  a  basin, 
within  a  few  feet  of  the  stove,  the  temperature  of  the  air  outside 
being  in  the  neighborhood  of  0°.  r\  he  spring  records  of  1886 
show  no  remarkable  features,  and  the  cool,  dry  summer  and 
pleasant  autumn  have  passed  in  the  same  manner. 

The  preceding  events  are  the  most  important  which  have 
occurred  in  the  history  of  the  Observatory.  Many  interesting 
meteorological  phenomena,  however,  have  not  been  described. 
Among  these  may  be  mentioned  the  wonderful  effects  of  cloud 
and  fog  the  latter  sometimes  covering  the  country  like  a  milky 
sea  from  whose  upper  surface  the  highest  hills  protrude  like 
islands,  the  glorious  sunrises  and  sunsets,  the  brilliant  moon- 
light scenes,  the  approach  of  thunder-storms  and  the  succeeding 
rainbows ;  all  these  sights  and  many  more,  which  not  one  in  a 
thousand  of  the  visitors  to  Blue  Hill  sees,  rarely  escape  the 
notice  of  the  weather-watcher,  and  render  a  sojourn  on  the  Hill 
interesting,  regarded  simply  for  the  scenic  effects. 


THE  STAFF  OF  THE  OBSERVATORY. 

This  consists  of  the  writer,  who  directs  the  work,  an  observer 
and  the  steward.  The  first  observer  was  Mr.  Willard  P.  Ger- 
rish,  whose  mechanical  skill  greatly  facilitated  the  setting  up  of 
the  instruments.  He  remained  a  year,  and  was  succeeded  by 
the  present  incumbent,  Mr.  H,  Helm  Clayton,  who  had  already 
become  known  by  his  writings  on  meteorological  subjects, 
while  at  the  Ann  Arbor  (Michigan)  Observatory.  He  is  an 
enthusiastic  meteorologist,  and  has  continued  his  investigations 
since  coming  to  Blue  Hill.  Last,  but  by  no  means  least,  so  far 
as  physical  welfare  is  concerned,  is  the  steward,  Frank  Brown, 
who  has  been  at  the  Observatory  almost  since  its  opening,  and 
has  satisfactorily  performed  his  duties,  at  times  under  difficul- 
ties. The  fact  that  there  has  not  been  a  day's  sickness  on  the 
part  of  any  of  the  inhabitants  of  the  Observatory,  testifies  better 
than  statistics  of  the  amount  of  ozone,  etc.,  to  the  healthful 
climate  of  Blue  Hill. 


METEOROLOGICAL  OBSERVATORY.  29 

Besides  the  above  persons,  the  Hill  colony  embraces  the  St. 
Bernard  "Alp," — a  true  weather  dog,  — and  a  varying  number 
of  cats  and  mice,  the  latter  taking  refuge  in  the  Observatory  in 
cold  weather.  The  current  expenses  of  the  Observatory  are 
about  twenty-five  hundred  dollars  a  year. 

FRIENDS    OF   THE   OBSERVATORY. 

Rev;  A.  K.  Teele  of  Milton  has  taken  an  active  interest  in  the 
enterprise  from  its  inception,  and  has  been  of  much  assistance 
in  looking  up  the  deeds  of  the  land  purchased.  Pleasant  rela- 
tions have  existed  with  the  United  States  Signal  Service.  Gen- 
eral Hazen,  Chief  Signal  Officer,  who  visited  the  Observatory 
last  August,  spoke  of  it  in  a  complimentary  manner,  and 
hoped  that  some  of  the  registering  apparatus  might  be  intro- 
duced at  the  Signal  Service  stations.  Professor  Abbe,  the  chief 
scientist  of  the  Washington  office,  has  visited  the  Observatory 
recently.  The  Signal  Service  observer  in  Boston,  Sergeant  O.  B. 
Cole,  and  his  associates,  have  been  uniform  in  their  courtesy. 
The  Council  of  the  New  England  Meteorological  Society,  includ- 
ing Professors  Niles,  Davis,  and  Upton,  and  Messrs.  Fitz  Gerald 
and  Weston,  have  done  much  to  aid  the  Observatory,  and  Dr. 
Draper,  the  director  of  the  New  York  Meteorological  Observa- 
tory, has  given  the  benefit  of  his  long  experience  with  recording 
apparatus.  The  eminent  meteorologists  whom  the  writer  met 
last  year  in  Europe  manifested  much  interest  in  this  Observa- 
tory, and  the  publications  of  some  of  the  foreign  stations  are 
received  in  exchange  for  the  hitherto  meagre  reports  of  its  work. 
It  is  for  these  friends,  as  well  as  for  many  others,  both  at  home 
and  abroad,  that  this  account  of  a  somewhat  unique  enterprise 
has  been  prepared. 

BLUE  HILL  METEOROLOGICAL  OBSERVATORY,  DECEMBER,  1886. 


